In order to comply with the increasingly stricter emission limits, it is essential in automotive technology to reliably detect defects in a tank ventilation system. This prevents fuel vapors from escaping unnoticed from the tank and fuel supply system.
A tank ventilation system as well as a method and a device for checking its operability is described in German Patent No. DE 41 26 880 A1. Here, the device includes an adsorption filter with a venting opening, a supply line to a tank, and a connecting line with an inserted tank vent valve to the intake manifold of the engine, as well as a temperature sensor for detecting the temperature of the adsorption material. Furthermore, there is a second temperature sensor in the tank ventilation system which is situated near the venting opening of the adsorption filter. The method for checking the operability of the tank ventilation system includes the following steps: initially, the temperature of the adsorption material is measured before the first regeneration of the material after a fueling operation. The temperature of the adsorption material is subsequently measured at a predefined point in time after the start of the first regeneration. Thereafter, the material temperature difference between the first and the second measured value is formed. Furthermore, the temperature of the venting air is measured before the first regeneration and at a predefinable point in time after the start of the first regeneration. The venting air temperature difference between the second and the first measured value is formed. By subtracting the venting air temperature difference from the material temperature difference, a regeneration temperature difference is obtained. This regeneration temperature difference is compared to a threshold value and the device is considered to be operational when the regeneration temperature difference exceeds the threshold value.